The MMM Knowledge Graph (20+ million RDF triples) can be downloaded from Zenodo: https://zenodo.org/record/4019643 (version 2.1.0, September 2020)
Technical documentation for the MMM project (including a set of SPARQL tutorials using the MMM data) can be found on GitHub:
https://mapping-manuscript-migrations.github.io/
Scripts and software for the MMM project are available here:
https://github.com/mapping-manuscript-migrations
The Sampo-UI software used for the MMM semantic portal is available here: https://github.com/SemanticComputing/sampo-ui